Processes for carbon-coating a substrate are known and are taught, for example, in U.S. Pat. No. 3,428,519 to Zvanut. Zvanut discloses a process for thermoplastic fiber generation and carbon-coating under atmospheric pressure in an oxygen-rich, closed system.
A second example of Boron-doped carbon-coating is taught in U.S. Pat. No. 3,565,683 to Morelock. Morelock discloses a continuous process for depositing a boro-carbon coating on an electrically heated surface of a pyrolytic carbon-coated fused silica fiber as it is passed through a liquid, thermally decomposable boron compound.
U.S. Pat. No. 4,722,860 to Doljack et al. discloses a method for forming a flexible carbon-coated, electrically conductive cloth. An organic compound is pyrolytically coated onto a refractory, fibrous cloth under an inert atmosphere, in a closed system. The use of a vacuum is disclosed as a means for mobilizing organic precursor compounds.
Processes for carbon densification of porous refractory materials are also known.
U.S. Pat. No. 4,196,159 to Brotzman et al. discloses a method for embedding carbon in the pores of refractory masonry used in furnaces and metallurgical vessels to re-carburize the masonry and extend its useful life. A carbon carrier is infiltrated under pressure into the heated masonry from its cooler outside surfaces. As the carrier penetrates the pores, cracks, and joints of the masonry, the increasing masonry temperature causes "cracking" of the carrier and the dissociated carbon is deposited in the masonry cavities. Carbon embedding occurs unevenly and takes place preferentially in zones of higher porosity, larger cavities, cracks, and joints.
U.S. Pat. No. 2,883,708 to Sem discloses a method for manufacturing carbon electrodes which reduces the porosity of such electrodes. A hydrocarbon gas is forced through the heated electrode body so that pyrogenic decomposition of the gas occurs and carbon is precipitated on and within the body to solidify the electrode. Densification is a function of the pressure and temperature differentials across the electrode body, of the size of the electrode body, and of the amount of gas forced through it.
EPO Patent No. 0 385 869, and corresponding U.S. Pat. No. 5,079,039 to Heraud et al., disclose a method for producing a ceramic matrix composite material having improved toughness. Alternating layers of an essentially ceramic material and a less rigid material such as pyrolytic carbon or boron nitride are deposited by chemical vapor infiltration on a porous reinforcing structure of refractory fibers to densify the structure and form the ceramic matrix composite material.
French Patent 2 401 888 also to Heraud et al. discloses a porous body partly densified by vapor deposition of carbon which is further densified by infiltration with refractory materials other than carbon. The densified body so produced has higher mechanical strength in tension and compression and is more resistant to erosion and chemical attack by molten alkali metals.